Network Working Group                                          R. Winter
Internet-Draft                                                       HSA
Intended status: Informational                                  S. Jeong
Expires: January 08, 2013                                           ETRI
                                                                JH. Choi
                                                             Samsung AIT
                                                           July 09, 2012

                  Towards an Energy-Efficient Internet


   Climate change and cost drives all sectors of industry and society as
   a whole towards more energy-efficient technology, products and life
   styles.  The collection of Internet infrastructure and the attached
   devices are a large user of electrical energy and therefore of course
   are no exception regarding this trend.  This memo attempts to
   identify obstacles and more importantly technology options for an
   energy-efficient Internet with a focus on the protocols that are the
   product of the IETF.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 08, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Conventions and Terminology  . . . . . . . . . . . . . . . . .  3
   3.  State of Affairs . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  The Current Network Energy Use . . . . . . . . . . . . . .  3
     3.2.  IETF/IRTF Work on Energy-Efficiency  . . . . . . . . . . .  3
     3.3.  Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Potential Obstacles for Realizing an Energy-Efficient Internet  5
     4.1.  Problems Caused by Sleep Modes . . . . . . . . . . . . . .  5
     4.2.  The Lack of Efficiency Metrics and Evaluation Methodologies 6
     4.3.  Problems due to Common Network Operation Practices . . . .  7
   5.  Potential IETF/IRTF Work Items . . . . . . . . . . . . . . . .  7
     5.1.  Load-adaptive Resource Management  . . . . . . . . . . . .  7
     5.2.  Energy-efficient Protocol Design . . . . . . . . . . . . .  8
     5.3.  Energy-efficiency Metrics and Standard Benchmarking
           Methodologies  . . . . . . . . . . . . . . . . . . . . . .  9
   6.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

1.  Introduction

   Regarding energy efficiency, many people regard the role of the
   Internet to be an enabler for it in sectors other than
   communications, e.g.  the potential for dematerialization (e.g.
   replacing letters with Email or DVDs with video streaming), the
   potential to reduce travel (e.g.  by allowing employees to work from
   home rather to commute to work or by replacing physcial meetings with
   video conferencing) just to name two areas.

   More recently, the energy use of the Internet itself, and more
   generally Information and Communication Technology (ICT), has
   attracted quite some attention which has lead to technologies such as
   Energy Efficient Ethernet [EEE] or the ProxZZZy Standard [PROXZZZY]
   and a large body of scientific publications.

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   The question is how can the IETF/IRTF help with existing and/or
   future protocol standards to support, exploit or enhance these
   developments that happen outside of the IETF. Even without these
   external technologies, can IETF protocols with or without
   modifications help to lower the energy use of the global Internet?
   This memo is intended to identify existing obstacles and potential
   places in the IETF protocol landscape where there is potential to
   achieve this goal: lowering the energy use of the Internet as a whole
   from end host to core router.

2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  State of Affairs

   Energy-efficiency certainly is important.  But is the Internet
   infrastructure a good place to look at and what is already out there
   that addresses energy-efficient communication?

3.1.  The Current Network Energy Use

   For a long time now, the Information Communications Technology (ICT)
   sector as a whole has experienced a rapid growth.  With this growth
   however comes a steep increase in power demand.  According to an
   ITU-T report [ITU] from 2008, wired and wireless networks consume a
   significant fraction of the overall electrical power.  Consequently,
   the fraction of green-house gas emissions that can be attributed to
   the ICT sector is significant and is currently estimated to be 2% of
   the overall man-made emissions.

   A report issued by the European Commission in 2008 [EC] is slightly
   more detailed regarding the energy use of ICT and makes forecasts
   regarding the development of the sector's energy use till 2020. In a
   scenario the report calls "business as usual" (BAU), the electricity
   consumption of ICT is predicted to double based on data from 2005.
   That equals over 10% of the total energy consumption in the 25 EU
   member states under observation.  It is this energy trend that is
   alarming.  It has to be noted however that consumer devices are part
   of this calculation but even when these devices are removed from this
   calaculation, the trend remains the same and over 50% of the energy
   budget remains.  Another large, and increasingly important consumer
   in this whole mix of technologies are data centers.

3.2.  IETF/IRTF Work on Energy-Efficiency

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   It would be wrong to say that energy-efficiency has not yet been
   considered within the IETF/IRTF. E.g.  during the 81st IETF meeting
   the very first IRTF Applied Networking Research Prize was awarded to
   work on energy-efficient traffic engineering [ANRP].  In addition the
   IETF EMAN working group is actively working on standards to measure
   and control energy-related aspects of powered entities.  Also, a
   growing number of internet drafts are being submitted that address
   energy issues and energy-efficiency such as [I-D.chakrabarti-
   nordmark-energy-aware-nd], [I-D.manral-bmwg-power-usage] and [I-D
   .okamoto-ccamp-midori-gmpls-extension-reqs] to name just a few.
   Finally, there are a number of other activities that face similar
   problems such as the Internet of Things [RFC6574] which likely would
   benefit from general energy-efficiency methods that are applicable in
   a wider context.

3.3.  Taxonomy

   The following represents a classification based on the one found in
   [GREENR] and lists examples for each category.

   o  Adaptive link rate technology: Most current types of network
      equipment show a constant power consumption profile largely
      irrespective of their actual utilization.  The computing world on
      the other hand has long embraced methods to approximate energy-
      proportional computing.  In the networking world we see first
      steps into energy-proportional communications.  Adaptive link rate
      technology is such a step where the energy use changes with link
      utilization.  The IEEE Energy Efficient Ethernet Task Force has
      devoted considerable efforts in this area and has published IEEE
      Std 802.3az-2010 (Amendment to IEEE 802.3-2008) [EEE].  The
      amendment describes modifications to existing physical layer
      specifications in order to make Ethernet more energy efficient.
      The amendment covers various technologies such as 10BASE-T or
      100BASE-TX. It also proposes a new Low Power Idle (LPI) mode and
      related mechanisms and protocols in order to energy efficiently
      manage Ethernet links.

   o  Network interface proxy technology: Proxying describes
      technologies that maintain network connectivity for other devices
      so that these can go into low power sleep modes.  This mainly
      targets the reduction of unnecessary energy waste through edge
      devices.  ECMA has published a proxying document [PROXZZZY].  This
      specification describes an overall architecture for network
      proxying and provides capabilities that a proxy may expose to a
      host.  Also, information that must be exchanged between a host and
      a proxy, and required and optional behavior of a proxy during its
      operation are described.

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   o  Energy-aware infrastructure: in order to achieve a further
      reduction in energy use, coordination and manangement of larger
      parts of the network appears to be a promising idea.  Energy-aware
      infrastructure describes a class of techniques to this end.
      Energy-aware routing is one example that falls into this category.
      Energy-aware routing makes use of the fact that traffic follows
      certain patterns.  Based on this knowledge, in times where network
      traffic is low, a number of routers can be put to sleep while the
      network as a whole still preserves connectivity and an adequate
      service level.

4.  Potential Obstacles for Realizing an Energy-Efficient Internet

   The following is a short list of problems that need to be addressed
   in order to introduce techniques that make the Internet more energy-

4.1.  Problems Caused by Sleep Modes

   A sleep mode is a kind of "deep" idle state which results in
   significant power savings but also requires a significant amount of
   time in order to wake the sleeping node up.  When not in use, network
   nodes could go to sleep in order to save power.  Sleep mode operation
   is a common practice e.g.  in cellular networks where mobile
   terminals spend most of their time in a sleep mode to conserve
   energy.  Many Internet protocols however could break if sleep modes
   would be introduced because they operate based on the assumption that
   the participating nodes are always-on [RFC4861] [RFC4862].

   Current networking services and applications are commonly designed to
   be fully available at all times with minimal response times.  If
   network nodes are allowed to go into a sleep mode, they effectively
   lose network connectivity and their applications and services stop
   working.  When these nodes wake up again, they have to re-initialize
   their applications and services potentially resulting in a non-
   negligible amount of signalling overhead [EEFI].

   Several IETF protocols require a node to keep constant network
   presence and process periodic or event-driven messages in order to
   maintain a persistent configuration or state.  For example, if an
   IPv6 node goes to sleep, it cannot perform Duplicate Address
   Detection (DAD) to defend its configured addresses.  In that case
   some other node may usurp its addresses [RFC4862].  Upon waking up,
   the node needs to go through a costly re-attachment procedure
   resulting in even larger delays until network connectivity is

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   Even when a node is idle with no running applications, background
   traffic is received that needs to be processed which inhibits the
   node from sleeping.  The good news is that common message exchanges
   during otherwise idle periods such as ARP processing or DAD, can
   either simply be dropped or be dealt with using minimal computational
   resources through a 3rd party - a Network Connectivity Proxy (NCP)
   [Wasserman] [SCE] [NCP].

   The issues described above can also be addressed by designing sleep-
   compatible protocols or by extending existing protocols (where
   possible) to include the ability to distinguish sleep form failure.

4.2.  The Lack of Efficiency Metrics and Evaluation Methodologies

   The mechanism side of energy-efficient protocol design is only one
   aspect that will lead to a greener Internet.  Another aspect is the
   evaluation of and the comparision between different possible
   approaches.  Currently, there is a lack of standard energy-efficiency
   metrics that are applicable to Internet protocols.

   There are a number of metrics and some of these actually attempt to
   quantify energy use with a direct reference to networking (e.g.  [I-D
   .manral-bmwg-power-usage]).  Right now however, it is challenging at
   best to perform an objective and useful comparision of mechanisms
   that attempt to increase the energy-efficiency of a protocol.

   Energy-efficiency is a metric that should be evaluated in a holistic
   way, taking into account consideration across various aspects of the
   network.  The central problem is that there is a looming danger that
   savings in one part of the network can be the cause for an increased
   use in another.

   In addition, the use cases can vary drastically which might call for
   a range of metrics each suitable for a different scenario.  For
   example, the energy-efficiency of data centers is commonly evaluated
   using the Power Usage Effectiveness (PUE) but there are many other
   metrics such as the IT Equipment Energy Efficiency (ITEE), IT

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   Equipment Utilization (ITEU), and so on [GGrid].  While many of these
   metrics have a significant value in isolation , a holistic
   methodology for measuring the energy-efficiency spanning multiple
   such metrics would be beneficial.

   The first big step, which to some degree is already been taken, is to
   assess current power consumption patterns and to come to an
   understanding how the power consumption is distributed in the
   network, in devices, in device components and how the utilization of
   the network impacts these patterns [PowerTrend] [GTC].

4.3.  Problems due to Common Network Operation Practices

   Many of the networks that constitute the Internet are over-
   provisioned and offer a large degree of redundancy, which, while
   contributing to the overall quality of the Internet service, results
   in low energy-efficiency.

   A lot of people feel that the QoS support of the Internet
   architecture itself is inadequate and see over-provisioning a the
   only sensible means to achieve it.  And indeed, it is a common
   practice.  Usually network traffic shows significant temporal
   fluctuations and, during low traffic periods, an over-provisioned
   network uses unnessecarily large quantaties of energy.

   Experimental measurements have showen that the energy consumption of
   some devices and components (such as Ethernet links) depend mainly on
   their capacity, not on actual utilization.  Most devices keep drawing
   a certain amount of power even in the absence of traffic, i.e.
   without providing a meaningful service.

   Moreover, for resiliency and fault-tolerance purposes, certain
   equipment is put into the infrastructure solely for backup purposes.
   Such redundancy also decreases the effective network energy-
   efficiency further [GREENR] [GTC] [EARTH].

   The above certainly is important and vital in many cases.  Often
   strong requirement make the above necessary (e.g.  switch-over times
   in the range of 50ms). It is not just a technical issue that needs to
   be solved here but also an issue of operation principles.  Putting
   nodes into sleep operation or incorprating energy-efficiency
   considerations into network operations will be challenging for the
   reasons stated above and there will be reluctance to allow energy-
   efficiency mechanisms to profoundly change the way networks are
   operated today.

5.  Potential IETF/IRTF Work Items

   The following is an (incomplete) list of potential work items where
   the IETF/IRTF might start to pave a path for energy-efficient
   protocol desgin and network operations.

5.1.  Load-adaptive Resource Management

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   In common networks that are provisioned for peak traffic load, a
   substantial amount of energy can be saved by dynamically allocating
   resources according to actual traffic.

   Conceptually, network resources may be shut down when there is no
   traffic or scaled down when there is little traffic to improve the
   overall energy-efficiency [GreenInternet].  Network equipment, such
   as base stations, may be turned off when there is no user within
   coverage or link capacity may be reduced when traffic demand is low.
   This type of approach potentially has a broad applicability to
   various areas not just wireless network, but also core routers/
   switches, optical transmission equipment and office networks.  Simply
   turning equipment off clearly would result in service degradation,
   instability and in the worst case loss of connectivity.  The overall
   optimization goal therefore is to minimize the network power
   consumption while maintain network performance resulting in a non-
   trivial contraint optimization problem [ANRP] [OptMgmt].

   In this area, the IETF/IRTF could work on algorithms to solve the
   above described optimization problem and on protocol support for it.
   Measuring and monitoring is already being worked on in the EMAN
   working group.  The control side, i.e.  acting on the measurements
   and configuring the network accordingly is still very much an open
   question.  While the EMAN MIBs allow control, the whole "how" is not
   addressed right now.  Also a set of best current practices can be

5.2.  Energy-efficient Protocol Design

   Energy-efficiency is one of these topics that need to be a design
   goal or otherwise it will be difficult to retrofit it into a protocol
   specification.  The question is what are the factors that need to be
   considered.  It might well be that there are certain design patterns
   and options that can be distilled that are vital and a protocol
   specification can be checked against these.  Such a list could be the
   product of the IETF/IRTF. The security aspects of the IETF underwent
   a similar evolution and security considerations are now a mandatory
   part of every new protocol specification.  This is not to say the
   there should be an Energy-Efficiency Considerations section in each
   new Internet draft, but there are a lot of lessons learned from this
   example.  There are a number of important security principles such as
   crypto-agility and it would be beneficial if something similar could
   be established for energy-effciency.  A trivial example would be to
   require that nodes can re-negotiate timeouts (in protocols that make
   use of timeouts) so that a node might be able to go into sleep mode
   or to attempt to synchronize periodic messages across a number of
   protocols so that these messages all fall into a certain timeframe
   and inbetween the node can sleep.

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   In addition, it IETF/IRTF could pick a number of existing protocols
   and attempt to extend them so as to make them more energy-efficient,
   or more likely allow the underlying technology to be more energy-
   efficient without breaking communication.  In some cases, entirely
   new protocols may be needed to support the sleep mode of nodes.

   Also, the IETF/IRTF can start to develop proxying solutions as
   discussed before.  Before going into sleep, a node delegates its
   functionalites to such a proxy, which will then respond to routine
   network traffic on behalf of the sleeping node and it will wake the
   node up when it is needed.  Proxys could handle traffic for network
   connectivity-related operations such as (ARP, ICMP, DHCP) and also
   proxy functions that are application specific could be developed
   (P2P). .  The IETF/IRTF would need to define the protocols and
   procedures for proxy operation such as discovery, selection,
   delegation and wake-up [SCE] [NCP].

5.3.  Energy-efficiency Metrics and Standard Benchmarking Methodologies

   Energy-efficient research and development needs standard performance
   metrics in order to evaluate and quantatively compare the
   effectiveness of energy-efficient solutions.

   Energy-efficiency of a network and the devices therein can be
   assessed using measures of energy per sent data unit (e.g.  in the
   unit of joule/bit) or power per date rate (watt/bps).  In principle,
   these measures indicate how much energy is needed to send a bit.
   Many approaches to network energy-efficiency are limited to the power
   consumption of a single device (router, switch or base station).
   This scope is comparably easy to specify and measure, but fails to
   capture performance aspects such as daily traffic fluctuation or
   network under-utilization [GTC].

   There are various options to approach this problem.  Energy-
   efficiency metrics could be extracted e.g.  from reference scenarios
   such as network topologies and traffic profiles (similar to what the
   automobile industry does).

6.  Conclusion

   Energy-efficiency cerainly is a buzz word right now but beyond the
   hype it indeed becomes an important economical and societal aspect.
   This document is an attempt to discern a number of work items in this
   space for the IETF/IRTF to consider.  While the IETF/IRTF is clearly
   not able to work on all of the above, some of the mentioned
   mechanisms are clearly more far reaching than others and some of the
   topics are surely outside of what the IETF/IRTF usually works on,
   there are a number of things that the IETF/IRTF can and should take
   on as work items to investigate.

   We present these ideas for discussion in the community and hope to
   extract a number of realistic action items to work on in the near

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7.  Security Considerations

   The draft covers a range of potential work items and research
   activities, each with its own security considerations.  These will be
   addressed once their actual form and nature become more concrete.

8.  IANA Considerations

   This document does not require any action from IANA.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2.  Informative References

   [ANRP]     Zhang, M., Yi, C., Liu, B. and B. Zhang, "GreenTE: Power-
              Aware Traffic Engineering", Proc.  IEEE International
              Conference on Network Protocols (ICNP) , October 2010.

   [EARTH]    "Energy-aware radio network technologies", https://www
     , .

   [EC]       "Impacts of Information and Communication Technologies on
              Energy Efficiency", September 2008.

   [EECDA]    Guan, K., Atkinson, G., Kilper, D. and E. Gulsen, "On the
              Energy Efficiency of Content Delivery Architectures",
              GreenComm4 , 2011.

   [EEE]      "802.3az-2010", IEEE std , 2010.

   [EEFI]     Bolla, R., Bruschi, R., Davoli, F. and F. Cucchietti,
              "Energy effciency in the future internet: A survey of
              existing approaches and trends in energy-aware fixed
              network infrastructures", IEEE Communications Surveys
              Tutorials , 2010.

   [GGrid]    Belady, C., "Green Grid Data Center Power Efficiency
              Metrics: PUE and DCiE", ,

   [GREENR]   Bianzino, A.P., Chaudet, C., Rossi, D. and J.-L. Rougier,
              "A survey of green networking research", IEEE
              Communications Surveys Tutorials , 2012.

   [GTC]      "Green Touch Consortium", , .


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              Gupta, M. and S. Singh, "Greening the Internet", ACM
              SIGCOMM , 2003.

              Chakrabarti, S., Nordmark, E. and M. Wasserman, "Energy
              Aware IPv6 Neighbor Discovery Optimizations", Internet-
              Draft draft-chakrabarti-nordmark-energy-aware-nd-02, March

              Manral, V., "Benchmarking Power usage of networking
              devices", Internet-Draft draft-manral-bmwg-power-usage-02,
              January 2011.

              Okamoto, S., "Requirements of GMPLS Extensions for Energy
              Efficient Traffic Engineering", Internet-Draft draft-
              okamoto-ccamp-midori-gmpls-extension-reqs-01, February

   [ITU]      "Resolution 73 - Information and communication
              technologies and climate change", October 2008.

   [NCP]      Jimeno, M., Christensen, K. and B. Nordman, "A Network
              Connection Proxy to Enable Hosts to Sleep and Save
              Energy",  Proc.  IEEE Internat.  Performance Computing and
              Communications Conf , 2008.

   [OptMgmt]  Lorincz, J., Capone, A. and D. Begusic, "Optimized network
              management for energy savings of wireless access
              networks", Computer Networks , 2011.

              "ProxZZZy for sleeping hosts", ECMA International
              ECMA-393, February 2010.

              Kilper, D., Atkinson, G., Korotky, S. K., Goyal, S.,
              Vetter, P., Suvakovic, D. and O. Blume, "Power Trends in
              Communication Networks", IEEE J  on Selected Topics in
              Quantum Electronics , 2011.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W. and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4862]  Thomson, S., Narten, T. and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC6574]  Tschofenig, H. and J. Arkko, "Report from the Smart Object
              Workshop", RFC 6574, April 2012.

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   [SCE]      Allman, M., Christensen, K., Nordman, B. and V. Paxson,
              "Enabling an Energy-Efficient Future Internet Through
              Selectively Connected End Systems", ACM SIGCOMM HotNets
              Workshop , 2007.

              Wasserman, M., "It's Not Easy Being 'Green'", IAB
              Interconnecting Smart Objects with the Internet Workshop ,

Authors' Addresses

   Rolf Winter
   University of Applied Sciences Augsburg
   An der Hochschule 1
   Augsburg 86161


   Sangjin Jeong
   138 Gajeongno, Yuseong
   Daejeon 305-700

   Phone: +82 42 860 1877

   JinHyeock Choi
   Samsung AIT
   FIL SAIT GiHeung
   Yongin 446-712

   Phone: +82 31 280 9589

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